JPS59179408A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce pattern noise and improve comfortability, by combining a plurality of main grooves on a tire tread with a plurality of sub grooves, and making a width of the sub grooves near tread side edges smaller than a width of the sub grooves at a tread central portion and near side walls. CONSTITUTION:Main grooves 6-9 are combined with sub grooves 11 and 12, and simultaneously the main grooves 6 and 9 are combined through sub grooves 10 with side walls 5, respectively. An angle theta of the sub grooves 10-12 relative to a circumferential direction of a tire is set to a value not more than 65 deg., and an opening width (a) of the sub grooves 10 and 11 opening to the main grooves 6 and 9 near tread side edges is set to a value smaller than an opening width (b) of the sub grooves 11 and 10 opening to a tread central portion A and the side wall portions 5 side, respectively. Thusly, the sub grooves 10 and 11 are made tapering, and it is possible to improve continuity in rigidity of block portions and sub groove portions in a block pattern. Accordingly, it is possible to reduce pattern noise due to discontinuity in rigidity and improve comfortability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire with low pattern noise and excellent comfort, and more specifically, the present invention relates to a pneumatic tire with low pattern noise and excellent comfort. A pneumatic tire that makes it possible to reduce turn noise by specifying the angle of the sub-groove connected to the main groove in the tread pattern and by varying the width of the sub-groove connected to the main groove near the ground contact edge. Regarding.

The noise generated when tires run is largely influenced by the tread pattern and is generally referred to as pattern noise. Numerous studies and improvements have been made in the past in order to reduce shiba-turn noise. These methods were mainly based on Q improvements such as the method of changing the minimum unit of repeating patterns on the tire circumference (hereinafter referred to as pinch), the type of pitch length, and the number of pitches on the tire circumference. .

However, although many of the methods proposed in the past have been able to reduce pattern noise, that is, pitch noise, in limited tread patterns, conventional methods cannot be used when the tread pattern is changed. This has the disadvantage that the effect of reducing pattern noise, that is, pitch noise, is lost.

Also, - this pattern noise, that is, pitch noise, tends to increase because of a tread pattern that has a plurality of main grooves extending in the circumferential direction of the tire and connects the main grooves with a sub-groove. This was particularly noticeable in block patterns. Furthermore, this terror pattern has an excellent ability to drain water that has entered between the tire tread and the road surface out of the tire tread, that is, it has excellent drainage ability, so it has excellent slip resistance on wet roads. However, as mentioned above, the pattern noise, that is, the pitch noise becomes harsh, so the comfort has to be sacrificed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire in which prosochronous turns are arranged on the tire tread, and furthermore, the two-turn noise is reduced.

To this end, the present invention provides a pneumatic tire with a round turn formed by a plurality of main grooves and a sub-groove opening into the main groove, in which the groove angle of the sub-groove with respect to the tire circumferential direction is 60" or less. The opening width a of the sub-groove that opens into the main groove located near the ground contact end is narrower than the opening width a of the sub-groove on the center side of the toe V and throat part, and on the side and wall part side,
The sub-groove is characterized in that it tapers toward the ground contact end.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory view showing the curved turn of the tire tread, and FIG. 2 is an explanatory cross-sectional view taken along the line X--X.

In Fig. 2, 1 is a tread part, 2 is a carcass mounted between a pair of left and right bead parts 4, 4, and a rubberized steel cord is attached to the tread part 1 so as to surround the outer periphery of this carcass 2. A belt layer 6 consisting of layers is arranged. 5° 5 is a pair of left and right sidewall portions connected to a pair of left and right beat portions 4, 4.

The block pattern shown in FIG. 1 is applied to the tread surface of the pneumatic tire shown in FIG. In Fig. 1, 6, 7, 8.9 are main grooves arranged in the circumferential direction of the tire;
Reference numerals 11 and 12 denote sub-grooves that connect the main grooves and open into the main groove.

Note that the sub-groove 10 is connected to the main groove 6 or 9 and opens to the sidewall portions 5, 5. A, B.

C is each block row located at the center of the tread portion, the second section, and a portion of the tread section. T represents the width of the tire contact surface (ground contact width). The groove angle θ of the minor grooves 10, 11, and 12 with respect to the tire circumferential direction (the angle formed by the main groove and the minor groove, measured on the acute angle side) is 60° or less. These sub-S1U.

Among 11 and 12, the main groove 6 is located near the grounding end.
The opening width a of the sub-groove 10.11 opening in the sub-groove 10.
, 11 is narrower than the opening width on the tread center side and sidewall side.

Therefore, in each of the block rows B and C of the yakant part and part of the shoulder, the angle θ1 formed by one side wall of the sub-groove with respect to the main groove and the angle θ2 formed by the other side wall of the sub-groove with respect to the main groove are θ1<6 □. Therefore, the sub grooves 10 and 11 become tapered toward the ground contact end. In order to further clarify these relationships, the main part of the minor groove is shown in an enlarged view in FIG. Note that in the block row A at the center of the tread portion, the angles are θ and 2θ2. In addition, in FIG. 1, the main grooves 6, 7, 8.9 are straight in the tire circumferential direction to improve drainage performance, and the groove depth D is 8 to 9.
It is mm. The groove depth 1 of the sub-grooves 10, 11, and 12 is within a range from 50% of the depth of the main groove to the same depth as the main groove.

The reason why the block pattern of the tread of the pneumatic tire is configured in this way is as follows.

That is, the sound generated while the tire is running, mainly pattern noise, is caused by the change in the rigidity of the tread pattern along the circumferential direction of the tire.

Therefore, in a block pattern, which is a pattern in which a plurality of main grooves are arranged in the circumferential direction of the tire and sub-grooves connecting the main grooves, the rubber that contacts the road surface is broken by the grooves, and these grooves alternately pass through the road surface. Therefore, the tread rigidity changes greatly in the tire circumferential direction, and pattern noise increases. For this reason, the present inventors conducted various experiments in order to eliminate the discontinuity in rigidity between the block part and the minor groove in the block pattern, and as a result, the angle between the minor groove and the main groove was brought closer to the circumferential direction. It has been discovered that by doing so, it is possible to substantially reduce the discontinuity in the stiffness of the entire tread surface, thereby making it possible to reduce pattern noise. In order to investigate the contribution rate to pattern noise between each rib (region made up of two major grooves), we created patterns in which each rib was blocked by a minor groove and a pattern in which it was not. As a result of comparative evaluation, it was found that the blocking of the rib by the sub-groove in the area near the ground contact edge caused pattern noise to increase due to high ground pressure. Based on these results,
As the experiment progressed further, it was found that the width of the minor groove connected to the main groove near the contact edge (this means both the minor grooves located in the ribs near the center of the tread and the ribs near the contact edge) It has been found that by applying this change, it is possible to substantially reduce the discontinuity in the stiffness of the entire tread surface, that is, it is possible to reduce pattern noise. Based on these results, the above block pattern was constructed.

Hereinafter, the effects of the present invention will be explained with reference to experimental examples.

Example (1) In a pneumatic tire having the block pattern shown in FIG. 1, the pattern when the angle θ formed by the main groove and the sub groove is uniformly changed for each block row of A, B, and C. The relationship with noise was tested. In this case, the tire size is 195/60 R14, the carcass is 2 layers of rayon at 90 degrees, the belt layer is 2 layers of steel at 24 degrees, a = 3+++ m in block row A, and a = 5 mm in block rows B and C. Finally, /b = 1 and d, and the measurement conditions were: tire internal pressure 2.0 K9/(go), load 300 kg, 6 km, running /h. The results are shown in Fig. 4.

In FIG. 4, the horizontal axis represents the angle θ, and the vertical axis represents the sound pressure level. The unit of sound pressure level is defbell (d
B).

As can be seen from FIG. 4, the pattern noise decreases as θ becomes smaller. In particular, when θ exceeds 60°, the discontinuity in tread stiffness becomes thicker and pattern noise increases. Therefore, θ needs to be 60'' or less.

(2) In the pneumatic tire having the block pattern shown in Fig. 1, the main grooves 6 and 9 located near the contact edge
The relationship with pattern noise when changing the groove width ratio (a/l) of the minor grooves 10 and 11 communicating with the groove was tested. In this case, in block row A, a=3 dragons, a/b-1,0=5
0", block rows B and C are 25mm, θ≦60
°. Other conditions are the same as in (1) above. The results are shown in FIG. In Figure 5, the horizontal axis is “
/b and vertical axis C represent sound pressure level (dB), respectively.

As is clear from Fig. 5, the smaller "/b", the more
In particular, when "/l) is 0.6 or less, the discontinuity of trend rubber that occurs between blocks becomes relatively smooth and pattern noise is reduced. Conversely, when "/b" exceeds 0.6 In some cases, the groove width a of the left and right sub-grooves connected to the main grooves 6 and 9 increases, which increases the discontinuity between blocks and increases pattern noise.

Therefore, it is preferable that /b<1 and a7b≦Q, 5.

In addition, in order to maintain anti-slip performance on wet road surfaces, especially drainage ability, if the groove width a of the sub-groove is too narrow, drainage resistance will increase, so in the case of a block pattern, it is required to be at least 2 mm. Furthermore, if "/b" is 10 or more (the sub-grooves taper toward the center of the tread portion and toward the outside of the ground contact edge), drainage performance deteriorates and the tire sways.

(3) The relationship between running speed and pattern noise was tested for the tires of the present invention and conventional tires.

In this case, the tire of the present invention is a pneumatic tire having a block pattern shown in FIG.
/60 R14, block row A'''ca/b-1, θ=
5σ, a = 3 mm, and block rows B and C
"/b = 0.6, θ1-49°, θ2 52°,
a=5 rum. The conventional tire is a pneumatic tire with a normal block pattern, where block row A is false = 1, θ = 65°, a = 3 mm, and block row B is
and in C”A = 1, θ = 65°, a = 5 mm
The tire size is also 195/60 R14
It is.

The test conditions were: air pressure 2.0 Kg/Crl, rim 6 JJ x 14, and load 350. The results are shown in FIG. In addition, in Fig. 6, the horizontal axis represents the speed (Km/hr
), the vertical axis represents the sound pressure level (dB), the solid line represents the conventional tire, and the dotted line represents the present invention tire.

As is clear from FIG. 6, it can be seen that the tire of the present invention has reduced pattern noise at all speeds compared to the conventional tire.

As described above, according to the present invention, it has a plurality of main grooves,
In a block pattern having a sub-groove connecting the main grooves, by defining the angle of the sub-groove connected to the main groove and varying the width of the sub-groove connected to the main groove near the ground contact edge, Since it is possible to improve drainage performance and reduce pattern noise, it is possible to provide a pneumatic tire with excellent noise characteristics without sacrificing good drainage performance on wet road surfaces.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram that does not show the main part of the block pattern of the tire tread, FIG. 2 is an explanatory diagram of the cross section taken along the line X-X, and FIG. 3 is an explanatory diagram that shows the main part of the sub-groove in an enlarged manner. Figure 4 shows the main groove,
An explanatory diagram that graphically shows the relationship between the angle θ formed by the minor groove and pattern noise. Figure 5 shows the relationship between the groove width ratio of the minor groove connected to the main groove located near the ground contact edge and the pattern noise. Fig. 6 is an explanatory diagram showing the relationship between the running speed and pattern noise in a graph. 1... Trend ff1s, 2... Carcass, 3...
...Belt layer, 4...Bead part, 5...Side wall part, 6°, 7, 8, 9...Main groove, 10, 11
．． 12... Minor groove, A, B, C... Block row, T.
... Tire contact surface, θ... Groove angle of the minor groove with respect to the tire circumferential direction, a, b... Width of the minor groove. Agent: Patent Attorney Shin Ogawa - Patent Attorney Ken Noguchi Patent Attorney Kazuhiko Saishita No. 4121

Claims (1)

[Claims] A pneumatic tire comprising a block pattern formed by a plurality of main grooves and a sub-groove opening in the main groove, wherein the groove angle of the sub-groove with respect to the tire circumferential direction is 60° or less,
The opening width a of the sub-groove that opens in the main groove located near the ground-contacting edge is narrower than the opening width of the sub-groove on the side of the tread portion center side and the sidewall portion, and the sub-groove tapers toward the ground-contacting edge. A pneumatic 9 tire that is characterized by its cylindrical shape.